Question

a worker can press on a 80 kg crate with a force of 600 newtons horizontally just before it starts to move. assuming the crate is on level ground, what must be the coefficient of static friction between the crate and the floor?
0.475
600
0.333
0.765
question 3
1 pts
which type of material would you expect to have the larger coefficient of friction, rubber or ice?
rubber
ice

Explanation:

Step1: Calculate the normal force

The normal force \(N\) on a level - ground object is \(N = mg\), where \(m = 80\space kg\) and \(g=9.8\space m/s^{2}\). So \(N=80\times9.8 = 784\space N\)

Step2: Use the formula for static friction

The maximum static - friction force \(F_s=\mu_sN\). Given \(F_s = 600\space N\) (the force just before the crate moves) and \(N = 784\space N\). We can solve for \(\mu_s\) using \(\mu_s=\frac{F_s}{N}\)
Substitute \(F_s = 600\space N\) and \(N = 784\space N\) into the formula: \(\mu_s=\frac{600}{784}\approx0.765\)

Rubber has a rougher surface texture compared to ice. Rougher surfaces generally have more inter - locking of surface irregularities, which leads to a greater resistance to sliding (higher friction). Ice, on the other hand, has a very smooth surface, especially when it is cold and free of debris.

Answer:

\(0.765\)